The present invention relates to an exposure head for use in an image recording apparatus, and more particularly to an exposure head for use in an image recording apparatus, which includes a plurality of light-emitting elements supported on a common support for reproducing an image on a recording medium, and a single optical system for converging light beams from the light-emitting elements onto the recording medium and superposing desired light beams accurately to produce a high-quality image on the image recording medium.
There has been proposed an image recording apparatus for reading color image signals recorded on a recording medium such as a floppy disc, an optical disc, or the like and reproducing a visible color image on another recording medium such as a sheet of photographic paper based on the color image signals.
In the proposed image recording apparatus, a plurality of light-emitting elements capable of emitting lights of different wavelengths are selectively energized in response to input image signals to generate the colors of cyan (C), magenta (M), and yellow (Y) on the color photographic paper.
A color image is reproduced by superposing light beams emitted from the respective light-emitting elements and controlled in their intensity levels on the color photographic paper in one area thereof.
In practice, an exposure head is employed to form a color image on a recording medium such as a sheet of photographic paper. The exposure head includes a plurality of supports supporting respective light-emitting elements and respective condenser optical systems. The supports are supported by a housing in an offset relation to a main scanning direction of the recording medium. The recording medium is wound around an image recording drum, which is then rotated in the main scanning direction, while the housing is moved in an auxiliary scanning direction substantially normal to the main scanning direction to form a two-dimensional color image on the recording medium.
In order to superpose light beams from the light-emitting elements to obtain a desired color, it is necessary to electrically control the timing for the light-emitting elements to emit their light beams dependent on the position where the image is to be recorded. Therefore, a control system required to control the timing is highly complex, and the cost of the entire image recording apparatus is high.
Reproduction of high-quality color images requires that mechanical adjustments should be made to converge the light beams from the light-emitting elements accurately in a desired position on the recording medium, in addition to the electric timing control described above. More specifically, the dimensions of the supports which support the respective light-emitting elements, the positions of the optical systems disposed on the supports, respectively, for converging or focusing the light beams onto the recording medium, and the dimensions of the housing, must be determined highly accurately. As a consequence, the process of manufacturing the exposure head is complex and time-consuming, and it is difficult to produce the exposure head economically.